1. Field of the Invention
This application is filed under 35 U.S.C. 371 and based on PCT/EP98/02920, filed May 1998, 1998.
This invention relates to a bleaching system of an enzyme which produces hydrogen peroxide and a transition metal compound and to the use of this system as a bleaching component in detergents.
2. Discussion of Related Art
Enzymatic bleaching compositions which contain a hydrogen peroxide generating system are known from the prior art and are described, for example, in patent applications EP 553 608, EP 553 607, EP 538 228, EP 537 381 and DE 20 64 146.
Enzymatic bleaching compositions of the type in question may be used, for example, in laundry detergents formulated to develop a good bleaching effect at low temperatures. In the wash liquor, the enzymes catalyze the reaction between the dissolved oxygen and the substrate.
A bleach activator is normally used in order to obtain a good bleaching effect at low temperatures, for example between 15 and 55xc2x0 C. One of the most commonly used bleach activators is tetraacetyl ethylenediamine (TAED) which forms peracetic acid by reacting with the hydrogen peroxide, the peracetic acid being the actual bleaching agent.
So far as the use of such bleach-containing enzymatic surfactant compositions is concerned, however, it is important that they contain little or no catalase because catalase catalyzes the decomposition of the hydrogen peroxide formed by the enzyme. Accordingly, the oxidase and also other enzymes in the system should be carefully purified which considerably increases the costs of the enzymes.
Oxidases are used in low concentrations for economic reasons. However, low oxidase or peroxidase concentrations also lead to the formation of less hydrogen peroxide and hence to a poor bleaching effect. Bleach catalysts in the form of transition metal complexes, for example of manganese (Mn) and/or iron (Fe), are known from the prior art and are described, for example, in European patent applications EP 0 458 397, EP 0 458 398, EP 0 544 519 and EP 0 549 272. In combination with hydrogen peroxide, they form a very powerful oxidation system.
Unfortunately, these transition metal complexes have the disadvantage that they destroy not only the bleachable soils, but also the dye present on the fibers. In some cases, they can even destroy the fibers themselves, resulting in so-called pitting.
The problem addressed by the present invention was to provide a catalyst system which would be effective at low temperatures without the external addition of oxygen carriers and which would react with bleachable soils present on the fibers or in the wash liquor, thus leading to the destruction of the soils. Although the bleaching system would react with free dye molecules present in the wash liquor, the color on the fabric would remain intact, i.e. reaction with the dye present on the fibers or with the fibers themselves would be avoided.
Accordingly, the present invention relates to a bleaching system of an enzyme which produces hydrogen peroxide and a transition metal compound, characterized in that an enzyme producing hydrogen peroxide from atmospheric oxygen and a suitable enzyme substrate is covalently bound to the transition metal compound.
Accordingly, the present invention also relates to the use of the bleaching system as a bleaching component in detergents and for inhibiting the transfer of dyes in the use of the detergents. The invention also relates to the use of the bleaching systems in disinfectants.
It has surprisingly been found that very good bleaching results are obtained at low washing temperatures, more especially between 15 and 55xc2x0 C., with the bleaching system according to the invention. The bleaching system continuously forms H2O2 and thus develops a uniform bleaching effect without causing any fiber damage. Although it reacts with the bleachable soils on the fibers and in the wash liquor and also with free dye molecules present in the wash liquor, it does not react with textile dyes present on the fibers.
At relatively high temperatures, the system is substantially inactive in view of the thermal lability of enzymes. By virtue of the high solubility of the enzymatic system according to the invention, deposits on fibers can be minimized. No deposits of the metal complex bound to the enzyme on items of laundry were observed.
The transition metal compounds used in enzyme-bound form in accordance with the invention are preferably copper, manganese, iron, cobalt, ruthenium and/or molybdenum compounds because the bleaching reaction can be controlled particularly well within certain limits with these compounds.